Outdated usage str.encode('rot-13') in rot13 codec

[Pix]

BPO	21171
Nosy	@malemburg, @terryjreedy, @ncoghlan, @pitrou, @vstinner, @benjaminp, @ezio-melotti, @merwok, @berkerpeksag, @serhiy-storchaka
Files	issue21171.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2014-04-17.03:33:28.319>
created_at = <Date 2014-04-07.16:25:51.849>
labels = ['type-bug', 'library']
title = "Outdated usage str.encode('rot-13') in rot13 codec"
updated_at = <Date 2014-04-17.03:33:28.318>
user = 'https://bugs.python.org/Pix'

bugs.python.org fields:

activity = <Date 2014-04-17.03:33:28.318>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2014-04-17.03:33:28.319>
closer = 'benjamin.peterson'
components = ['Library (Lib)']
creation = <Date 2014-04-07.16:25:51.849>
creator = 'Pix'
dependencies = []
files = ['34757']
hgrepos = []
issue_num = 21171
keywords = ['patch']
message_count = 5.0
messages = ['215712', '215733', '215944', '216005', '216017']
nosy_count = 12.0
nosy_names = ['lemburg', 'terry.reedy', 'ncoghlan', 'pitrou', 'vstinner', 'benjamin.peterson', 'ezio.melotti', 'eric.araujo', 'python-dev', 'berker.peksag', 'serhiy.storchaka', 'Pix']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue21171'
versions = ['Python 3.4', 'Python 3.5']

[Pix]

Function rot13 in file "encodings/rot_13.py" throws exception:

LookupError: 'rot-13' is not a text encoding; use codecs.encode() to handle arbitrary codecs

[berkerpeksag]

Here's a patch. I tested it with the following command:

    $ cat LICENSE | ./python -m encodings.rot_13

[terryjreedy]

Since rot_13 is a transcoder, not an encoder, the error message is correct, as is the fix for the function. However, since neither the module encodings.rot_13 nor the rot13 function in the module are documented, (not even in 2.7), I wonder if the function and the if __name__; clause are ancient holdovers that should be removed. In other words, I am not sure if Berker's test is currently a supported usage. I remember that there was some discussion on pydev about how much to add back but not the details.

[serhiy-storchaka]

LGTM.

[python-dev]

New changeset a81f0caab279 by Serhiy Storchaka in branch '3.4':
Issue bpo-21171: Fixed undocumented filter API of the rot13 codec.
http://hg.python.org/cpython/rev/a81f0caab279

New changeset f86504da2fcc by Serhiy Storchaka in branch 'default':
Issue bpo-21171: Fixed undocumented filter API of the rot13 codec.
http://hg.python.org/cpython/rev/f86504da2fcc